package gr.teiath.newsfeed;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import android.content.Context;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;



	public class DBHelper extends SQLiteOpenHelper{
		 
	    //The Android's default system path of your application database.
	    private static String DB_PATH = "/data/data/gr.teiath.newsfeed/databases/";
	 
	    private static String DB_NAME = "DB.sql";
	 
	    private SQLiteDatabase myDataBase; 
	 
	    private final Context myContext;
	 
	    /**
	     * Constructor
	     * Takes and keeps a reference of the passed context in order to access to the application assets and resources.
	     * @param context
	     */
	    public DBHelper(Context context) {
	 
	    	super(context, DB_NAME, null, 1);
	        this.myContext = context;
	    }	
	 
	  /**
	     * Creates a empty database on the system and rewrites it with your own database.
	     * */
	    public void createDataBase() throws IOException{
	 
	    	boolean dbExist = checkDataBase();
	 
	    	if(dbExist){
	    		//do nothing - database already exist
	    	}else{
	 
	    		//By calling this method and empty database will be created into the default system path
	            //of your application so we are gonna be able to overwrite that database with our database.
	        	this.getReadableDatabase();	        	
	 
	        	try {
	 
	    			copyDataBase();
	 
	    		} catch (IOException e) {
	 
	        		throw new Error("Error copying database");
	 
	        	} finally {
	        		this.close();
	        	}
	    	}	 
	    }
	 
	    /**
	     * Check if the database already exist to avoid re-copying the file each time you open the application.
	     * @return true if it exists, false if it doesn't
	     */
	    private boolean checkDataBase(){
	 
	    	SQLiteDatabase checkDB = null;
	 
	    	try{
	    		String myPath = DB_PATH + DB_NAME;
	    		checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
	 
	    	}catch(SQLiteException e){
	 
	    		//database does't exist yet.
	 
	    	}
	 
	    	if(checkDB != null){
	 
	    		checkDB.close();
	 
	    	}
	 
	    	return checkDB != null ? true : false;
	    }
	 
	    /**
	     * Copies your database from your local assets-folder to the just created empty database in the
	     * system folder, from where it can be accessed and handled.
	     * This is done by transfering bytestream.
	     * */
	    private void copyDataBase() throws IOException{
	 
	    	//Open your local db as the input stream
	    	InputStream myInput = myContext.getAssets().open(DB_NAME);
	 
	    	// Path to the just created empty db
	    	String outFileName = DB_PATH + DB_NAME;
	 
	    	//Open the empty db as the output stream
	    	OutputStream myOutput = new FileOutputStream(outFileName);
	 
	    	//transfer bytes from the inputfile to the outputfile
	    	byte[] buffer = new byte[1024];
	    	int length;
	    	while ((length = myInput.read(buffer))>0){
	    		myOutput.write(buffer, 0, length);
	    	}
	 
	    	//Close the streams
	    	myOutput.flush();
	    	myOutput.close();
	    	myInput.close();
	 
	    }
	 
	    public void openDataBase() throws SQLException{
	 
	    	//Open the database
	        String myPath = DB_PATH + DB_NAME;
	    	myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
	    		 
	    }
	 
	    @Override
		public synchronized void close() {
	 
	    	    if(myDataBase != null)
	    		    myDataBase.close();
	 
	    	    super.close();
	 
		}
	 
		@Override
		public void onCreate(SQLiteDatabase db) {
	 
		}
	 
		@Override
		public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
	 
		}
	 
	    
		
		
		
		// Add your public helper methods to access and get content from the database.
	       // You could return cursors by doing "return myDataBase.query(....)" so it'd be easy
	       // to you to create adapters for your views.
	 
	}

